He was a respected celebrity biographer who wrote bestselling bios on personalities like JFK, Bobby Kennedy, Jackie Kennedy Onassis, Elizabeth Taylor, Marilyn Monroe, and Joe DiMaggio.

His advances were generous, his work generally respected, and his career as a literary biographer successful, with reviewers calling his works “engrossing,” “well-researched,” and “riveting.”

Yet it turns out many of the books the late C. David Heymann wrote, including his last, “Joe and Marilyn: Legends in Love,” were fabricated and riddled with egregious errors, according to a new expose by Newsweek magazine.

“[A]ll the celebrity bios Heymann wrote for [Simon & Schuster] and other publishers – dealing with JFK, Bobby Kennedy, Jackie Kennedy Onassis, Elizabeth Taylor and Marilyn Monroe – are riddled with errors and fabrications,” writes David Cay Johnston in his exposé, “C. David Heymann’s lies about JFK and Jackie, Marilyn Monroe and Elizabeth Taylor.” “An exhaustive cataloging of those mistakes would fill a book, so a sampling from his long career will have to suffice.”

Johnston then goes on to chronicle a series of forgeries and fabrications, from passing off interviews conducted by others as his own to claiming he had spoken to sources when he hadn’t, to exaggeration, errors, and outright fabrication of sources and stories.

Writing about Heymann’s 1983 hit, “Poor Little Rich Girl,” about Barbara Hutton, Johnston writes, “The book spun out lurid tales that collapsed with just a phone call or two. Without much effort, I found nine people named in the book or known to have been involved in events mentioned in the book, including the legendary actor Cary Grant, who was once married to Hutton. All disputed Heymann’s account.”

When Johnston confronted Heymann and his publisher on this, and other, books, he received a series of excuses: Heymann said he had no tape recordings, no paper trail of plane tickets and lodging receipts, and no recollection of how to find various locations where he had allegedly conducted research and interviews.

And yet, “Poor Little Rich Girl” was a hit, made Heymann hundreds of thousands of dollars, and even became an NBC television movie that won three Emmys and a Golden Globe.

After a top Hollywood lawyer threatened litigation due to the book’s fabrications, Random House withdrew the bestseller and pulped as many copies as it could recover.

Nonetheless, Heymann went on to write other bestselling bios, including “A Woman Named Jackie,” “Liz: An Intimate Portrait of Elizabeth Taylor,” “RFK: A Candid Biography of Robert F. Kennedy,” “American Legacy,” ‘Bobby and Jackie: A Love Story,” and his last book, “Joe and Marilyn.”

That final book, a titillating tale about the troubled love life and brief marriage of Joe DiMaggio and Marilyn Monroe, received positive reviews from outlets like the New York Post, the Columbus Dispatch, Kirkus Reviews, and The Christian Science Monitor.

The book was full of juicy details. “Heymann wrote that DiMaggio beat Monroe, wiretapped her home and stalked her by skulking around in disguises, wearing a fake beard and for hours holding up a copy of The New York Times so no one would notice him in the lobby of the Waldorf Astoria hotel,” Johnston writes.

He goes on to list a series of problems with the book: interviews with sources who were dead by the time Heymann began work on the bio, sources who said they never actually spoke to Heymann, sources who said Heymann wrote “dramatic lies,” and stories Heymann himself contradicted in his other books.

For example, Heymann cites Joe DiMaggio Jr. the slugger’s son, as a source on more than 50 of the book’s 393 pages. The only problem? Joe Jr. died in 1999, long before Heymann started work on the book, Johnston writes.

These are Johnston’s assertions. Of course, Heymann isn’t alive to defend himself, his sources, or his works.

His editor and publisher appear to stand by the late biographer’s accounts, however. Emily Bestler, Heymann’s editor, has said that she paid to have his final book thoroughly fact-checked and that it came out clean.

After conducting his own investigation, Johnston doesn’t buy it.

“Most publishers rely on their authors to be truthful, and diligent in their research, and most nonfiction books are not fact-checked by publishers,” he writes. “But when a red flag is raised, publishers have an obligation to their readers to investigate. And when a sea of red flags floods their lobby, they need to start pulping the fiction.”